758
tar -vczfx123 ought to do it
(imgs.xkcd.com)
img title="I don't know what's worse--the fact that after 15 years of using tar I still can't keep the flags straight, or that after 15 years of technological advancement I'm still mucking with tar flags that were 15 years old when I started."
I don't remember the last time I had to worry about the compression. I simply run
tar xf myfile.tar.whateverand it works every time.